1. Field of the Invention
The present invention relates to display apparatus using a plasma display panel (PDP) known as a thin and light display having a larger screen.
2. Background Art
In a plasma display panel, phosphor is excited by ultraviolet rays, which are generated by gas discharge, and emits light, thereby making a color display.
The plasma display apparatuses are classified into two driving systems, i.e., an AC type and a DC type, and classified into two electric discharge systems, i.e., a surface discharge type and an opposed discharge type. A three-electrodes type and surface discharge type plasma display apparatus becomes a mainstream, because of high resolution, a large display and easy manufacturing for simplicity of its structure. FIG. 8 shows a common structure of a panel section of the plasma display apparatus.
A first board includes scanning electrode 2 and sustain electrode 3 which are disposed at an interval of MG (hereinafter referred to as a “main discharge gap MG”) on transparent and insulating substrate 1, e.g., a glass, to form a first board. A plurality of scanning electrodes 2 and sustain electrodes 3 are disposed at intervals of IPG (hereinafter referred to as an “inter pixel gap IPG”) in pairs. Dielectric layer 4 and protective film 5 are formed in a manner to cover scanning electrode 2 and sustain electrode 3. A second board includes a plurality of data electrodes 7 which are disposed on insulating substrate 6, e.g., a glass, and dielectric layer 8 covers data electrodes 7. On dielectric layer 8, barrier rib 9 is disposed between data electrodes 7, and parallel thereto. Phosphor 10 is formed on a surface of dielectric layer 8 and sides of barrier rib 9. Substrate 1 and substrate 6 confront each other in a manner that scanning electrode 2 and sustain electrode 3 cross data electrode 7 at right angles, so that a section where a pair of scanning electrode 2 and sustain electrode 3 crosses data electrode 7 becomes discharge cell 11. Xenon gas and at least one of helium, neon and argon gas are sealed as discharge gas in discharge cell 11.
FIG. 9 illustrates a schematic view of a driver, which outputs a driving voltage for driving the panel section shown in FIG. 8, and a wire connecting state for electrodes of the panel section. Arrangement of the electrodes of the panel section constitutes an m by n (m×n) matrix. Data electrodes 7 with m columns are arrayed in a column direction for addressing, and scanning electrodes 2 and sustain electrodes 3 with n rows are arrayed in pairs and in a row direction for keeping discharge.
The driver includes data-writing-driving circuit 12, scanning-electrode-driving circuit 13, initializing circuit 14 and sustain-electrode-driving circuit 15. Data-writing-driving circuit 12 is a circuit for outputting the driving voltage to data electrode 7, and is coupled to data electrodes 7 with m output terminals. Scanning-electrode-driving circuit 13 is a circuit for outputting the driving voltage to scanning electrode 2, and is coupled to scanning electrodes 2 with n output terminals. Sustain-electrode-driving circuit 15 is a circuit for outputting the driving voltage to sustain electrode 3, and is coupled to sustain electrode 3 in common. Initializing circuit 14 is a circuit for executing initializing action, namely, driving action for storing initial charge to each electrode, which has no charge before energization.
However, in the plasma display apparatus, which has the panel section and the driver, discussed above, when a discharge-cell pitch is reduced for high resolution, false discharge tends to be generated in Y direction of the panel section shown in FIG. 8.
The reason of the mechanism is considered as follows. After the last sustaining discharge is applied, for example, a wall voltage of a surface of protective film 5 on scanning electrode SCNi changes from negative to positive. This state is achieved by positive ions which reach the surface of protective film 5. However, mobility of positive ions (referred to as “μion”) is much slower than mobility of electrons (referred to as “μe”). Therefore, for example, the wall voltage near main discharge gap MG is easily changed because positive ions do not need to move a long distance. However, positive ions have to move a long distance at an outside of scanning electrode SCNi, i.e., near inter pixel gap IPG, whereby probability that positive ions do not reach the surface of protective film 5 becomes high. As a result, negative electric charges 16 are not neutralized and remain at the outside of scanning electrode SCNi, i.e., near inter pixel gap IPG. FIG. 10A shows the state discussed above and a sectional view of FIG. 8 taken along the line 10A—10A. In this drawing, the reference mark “+” or “−” shows an electric charge, however, the drawing shows only a concept, and does not show the actual number of electric charges.
The following operations are executed with unnecessary negative electric charge 16 kept near inter pixel gap IPG. In this state, scanning pulse voltage Vad is applied to scanning electrode SCNi, and writing pulse voltage Vw is applied to data electrode Dj by a writing operation in a writing period. At that time, as shown in FIG. 10B, discharge 17 is generated between data electrode Dj and unnecessary negative electric charge 16 near inter pixel gap IPG, so that large amounts of priming-effect particles, e.g., metastable atom or ion, are generated according to discharge 17. Priming-effect particles tend to flow into inter pixel cells because a place, where discharge 17 is generated, is near inter pixel gap IPG. This phenomenon remarkably occurs in a case where a pitch of discharge cell 11 is narrow. As shown in FIG. 8, there is no barrier such as barrier rib 9, which prevents discharge in X direction, in Y direction, so that priming-effect particles mainly flow into inter pixel cells in Y direction, and change a wall voltage of discharge cell 11. As a result, false discharge, which causes a writing-error or -reject, occurs in Y direction.